net is a namespace alias for boost::asio:

The namespace alias beast::net replaces boost::asio in all code
and documentation.

example/cppcon2018/net.hpp

@@ -12,8 +12,7 @@
 
 #include <boost/asio.hpp>
 
-namespace net = boost::asio;                    // namespace asio
-using tcp = net::ip::tcp;                       // from <boost/asio/ip/tcp.hpp>
-using error_code = boost::system::error_code;   // from <boost/system/error_code.hpp>
+namespace net = boost::asio;                    // from <boost/asio.hpp>
+using tcp = boost::asio::ip::tcp;               // from <boost/asio/ip/tcp.hpp>
 
 #endif